The present invention relates to mixtures comprising itaconic acid or itaconic acid derivatives and primary amines, and to the use thereof as a starting material for the preparation of 1,3- and 1,4-alkylmethylpyrrolidones.
The present invention further relates to a process for preparing 1,3- and 1,4-alkylmethylpyrrolidones by reacting inventive mixtures with hydrogen in the presence of hydrogenation catalysts. The present invention further provides mixtures comprising 1,3-alkylmethylpyrrolidone and 1,4-alkylmethylpyrrolidone, and for the use of these mixtures.
N-alkylpyrrolidones are important products in the chemical industry, which are used in a multitude of applications.
N-alkylpyrrolidones are thermally stable, chemically substantially inert, colorless, low-viscosity and aprotic solvents with wide usability. For instance, N-methylpyrrolidone (NMP) and N-ethylpyrrolidone (NEP) and the higher homologs are usable as solvents, diluents, extractants, detergents, degreasers, adsorbents and/or dispersants.
NMP finds use in the extraction of pure hydrocarbons in petrochemical processing, in the purification and removal of gases such as acetylene, 1,3-butadiene or isoprene, in aromatics extraction, for example in the Distapex process of LURGI GmbH, in acidic gas scrubbing and in lubricant oil extraction. In addition, NMP can be used as a solvent for polymer dispersions, for example for polyurethane dispersions.
NMP is also a good solvent for many polymers such as polyvinyl chloride (PVC), polyurethanes (PU), acrylates or butadiene-acrylonitrile copolymers, and is used in the processing thereof.
NMP is also used as a detergent in the removal of paint and coating residues, and as a pickling agent and as a detergent for metal, ceramic, glass and plastic surfaces.
NMP is likewise a solvent or cosolvent for the formulation of active ingredients in crop protection.
NEP and other N-alkylpyrrolidones can replace NMP in many applications and, furthermore, in many cases exhibit additionally advantageous properties (WO-A-2005/090447, BASF SE).
The preparation of N-alkylpyrrolidones is known.
N-alkylpyrrolidones can be obtained, for example, by reacting gamma-butyrolactone (γ-BL) with monoalkylamines to release one equivalent of water, for example analogously to Ullmann's Encyclopedia of Industrial Chemistry, Volume A22, 5th ed., p. 459 (1993), or analogously to DE-A-19 626 123 (BASF SE).
It is equally possible to prepare N-alkylpyrrolidones from maleic anhydride or other dicarboxylic acid derivatives and monoethylamines in the presence of hydrogen and a hydrogenation catalyst, for example according to EP-A-745 598 (Bayer AG) oder WO-A-02/102773 (BASF SE).
In addition to N-alkylpyrrolidones, substituted N-alkylpyrrolidones are also known. The substitution allows the application and processing properties of the N-alkylpyrrolidones to be modified.
One example of such a modification is that of N-alkylpyrrolidones with one or more alkyl substituents which are bonded to positions 3 and 4 of the pyrrolidone ring. Alkyl-substituted N-alkylpyrrolidones can be prepared, for example, according to the disclosure of EP-A1-0027022 by reacting alkylamines and hydrogen with substituted cyclic anhydrides/imides in the presence of ruthenium catalysts.
WO-A1-2005051907 discloses the reaction of dicarboxylic acids or derivatives thereof with hydrogen and amines in the presence of ruthenium or osmium catalysts.
U.S. Pat. No. 4,731,454 describes the reduction of cyclic imides over cobalt catalysts to obtain the corresponding N-alkylpyrrolidones.
The reaction of saturated cyclic carboximides or of saturated ammonium salts of the dicarboxylic acids in the presence of carbon-supported noble metal catalysts is disclosed in WO 02/102772.
DE-A1-1620191 describes the reaction of alkylsuccinic acid with primary amines and hydrogen in the presence of a hydrogenation catalyst to give the corresponding N-substituted derivatives of α-pyrrolidones which are alkylated on the carbon atoms in positions 3 and/or 4.
The references cited above disclose only the use of saturated dicarboxylic acids and dicarboxylic acid derivatives, and of dicarboxylic acids or dicarboxylic acid derivatives which have an unsaturated main chain, such as maleic acid and derivatives thereof, as suitable starting materials for the preparation of pyrrolidones. It is not stated that dicarboxylic acids or dicarboxylic acid derivatives which have an unsaturated side chain or even a terminal double bond in the side chain can be converted to the corresponding pyrrolidones.
One example of a dicarboxylic acid having an unsaturated terminal side chain is itaconic acid.
It is known that the reaction of itaconic acid with primary amines forms, in an exothermic reaction, the corresponding 4-carboxypyrrolidones or 4-carbamidopyrrolidones, which form through addition of the primary amines onto the unsaturated side chain (see Imamura et al., Chemical & Pharmaceutical Bulletin (2004), 52(1), 63-73, Paytash et al., Journal of the American Chemical Society (1950), 72, 1415-1416 and Southwick et al., Journal of Organic Chemistry (1956), 21, 1087-1095). Accordingly, the direct reaction of itaconic acid with primary amines and hydrogen to give the corresponding pyrrolidones is not disclosed, since the formation of the 4-carboxypyrrolidones or 4-carbamidopyrrolidones sets in before the hydrogenation to the desired pyrrolidones occurs.
Nitrogen-containing derivatives of itaconic acid, such as the amides or imines thereof, may also react under the conditions of the hydrogenation with addition of the nitrogen onto the double bond to give undesired cyclic by-products.
By virtue of this reactivity, itaconic acid and derivatives thereof differ significantly from their structural isomers citraconic acid and mesaconic acid and derivatives thereof, which have an unsaturated main chain and can therefore be converted by the methods described in the above references to alkylmethylpyrrolidones.
In order nevertheless to be able to use itaconic acid as a starting material for the preparation of methyl-substituted N-alkylpyrrolidones, 2-methylsuccinic acid, according to the teaching of DE-A1-1620191, can be reacted with primary amines with hydrogen in the presence of hydrogenation catalysts. 2-Methylsuccinic acid can in turn be prepared by hydrogenation of itaconic acid (CN-A1-1609089). This means that, however, before the reaction of 2-methylsuccinic acid with primary amines to give pyrrolidones, the 2-methylsuccinic acid starting material has to be obtained in a preceding reaction stage.